Endless belt conveyer



March 20, 1928. v'

T. c. FENNARD mmnnss *BELT couvmsn 'Filed July 2. 1927 Patented Mar. 20,-1/9284.

UNITED STATES 1,663,344'. APATENT OFFICE.

THOMAS CAYGILL LENNARI),y F GLASGOWQSCOTLAND.

ENDLEss BELT coNvEYER.

Application filed July 2, 1927, Seria1.No. 203,134, and in Great Britain Hay 21, 1926.

This invention relates to improved tensioning means for endless belt conveyers or elevators and has primarily 'for its object to enable the tension on the belt t0 be varied 5 in-relation to the load, sothat the tension is automatically or mechanically reduced when the load is low and increased as the load 'increases.

At presentit is usual to allow for stretch I and normal loading of the belt by applying initial tension to the belt by means of screw .or ratchet mechanism, or by the use of weights. AIn such cases, the tension when once adjusted remains constant.

` 5 'My invention may be employed either alone orin conjunction with the usual initial tensioning means. y v' According to the present invention, Ifprovide yan adjustable or slidable belt-tensioning device connected to an auxiliary reciprocatory compressed-air or other lluid pressure 1 engine, means being provided for either maintaining constant pressure in the engine or. adjusting the pressure to vary theiposition of the belt-tensioning device. The pressure may be controlled by fluctuations in the load on the belt drive, so as toautomatmally increase the tension on the belt as the load y increases and vice-versa.l

My invention is more particularly appl1c able to endless belt conveyers for colliery workings, for which purpose compressed-au is used as the pressure fluid for driving the auxiliary engine. To this end, an air com- 35. pressor may be driven' from the usual head or tail pulley or driving motor of the conveyer or the supply may be taken from an independently driven compressor, the compressor being connected to the cylinder of the auxiliary engine through a receiver and control valve.

The accompanying drawing illustrates one example of my invention in its appllcation to an electrically-driven endless belt conveyer,

Figs. 1 and 2 being diagrammatic views showing the conveyer and belt tensioning mechanism in plan and elevation respectively. Fig. 3 is a detail sectional elevation of the valve and Fig. 4 a vertical sectional View through the auxiliary engine.

. In the example illustrated, the main 'current Vsupply a to the driving motor A of the conveyer is in series with an electro-magnet or other electrical device B controlling a valve C 'in a. pressure-fluid supply pipe D receiver R.

The stem c of the control valve C` is controlled by the electro-magnet Bl in series 'lo` with the main current supply a to the drivmg motor A of the conveyer. The piston rod f of the piston F of the auxiliary engine may be coupled to the tail pulley ory adjustable roller G of the conveyer, the tail 76 pulley or adjustable roller G being mounted upon a slide H to which the; piston of the auxiliary engine' is fixed. The slide H is mounted upon aimain slidelbed K upon which the cylinder Eis fixed and which is so operated by screws L or other mechanism to enable the initial tension on the belt M vto be adjusted as desired.

@The supply of the compressed-air to the auxilia engme isthuscut-ol. When the load on t e conveyer increases, the current used 05 will alsoincrease and thus increase the excitation of the ,electro-magnet B until it opens the valve C and admits compressed- 'air to the auxiliary engine E, whereupon the piston F of the aux1liary engine will be driven outwards, thereby increasing the tenj sion on the belt M, by drawing the tail pulley G along its slide4 bed K.

The cylinder E of the auxiliary engine'is preferably fitted with an ad'ustable relief cock `0r vent V. which will allow the air in the cylinder to escape at a. predetermined rate. 1

' When the load on the conveyer ,decreases the electro-magnet B will allow the control l110 l valve C to reduce or cut-oil the air supply lil to the auxiliary engine E and the pressure in the cylinder will thus be reduced, thereby releasing the tension' on the belt M.

en the belt is loaded, the compressedair in the cylinder E forms a cushion and serves to absorb heavy shocks due to sudden increases in the load, as for example, when large pieces of material fall on to the belt. The belt is thus enabled to accommodate itself readily to the varying load conditions. P designates a manually-actuated valve *which maybe fitted in the pressure pipe D. T designates the idler rollers (some only of which are shown) for supporting the belt M.- i

lt will'be understood that the pressure pipe connection from the control'valve C to the cylinder E of the auxiliary engine must be flexible or otherwise designed to allow vof adjustment of the auxiliary engine when adjusting the initial tension on the belt. In

the example shown, a flexible pipe d connects the valve D to the inlet connection e of the cylinder E.

M invention can also be applied to any num r of conveyers, one common compressor .supplying a group of receivers, each connected to its `own control valve, and each valve being connected to its own auxiliary engine for adjusting the tension ofthe corres endingl conveyer.

y invention may also be employed Withont the provision of an automatically-controlled valve C. In this event, the compresser N may be adapted to maintain a constent pressure in the engine cylinder E and the pressure in the cylinder E may be adjusted by the provision of a manually-con-- trolled valve, such as the valve P.

l claims Il. In electrically-driven endless belt conveyers, a belt tensioning device, a fluidpressure engine connected thereto, a pressure Huid supply pipe connected to the engine, a valve controlling the pressure fluid supply, and means controlling said valve and actuated by fluctuations in the current supply to the driving motor of the conveyer.

2. Tensioning means for endless belt conveyers comprising a reciprocatory fluid pressure piston engine, a piston therein connected to the tail pulley of the conveyer, a bed upon which said engine and said tail pulley are mounted, said pulley being movable on said bed in response to movement of said piston, and means for initially adjusting said bed, to initially tension the belt.

3. Improved tensioning means for endless belt conveyers or elevators comprising an adjustable belt tensioning device, a reciprocatory fluid-pressure engine connected thereto, and means responsive to fluctuations in the load on the vbelt drive for adjustinfr the fluid pressure to vary the position o? the belt tensioning device.

4. Improved tensioning means for endless belt conveyers or elevators comprising an adjustable belt tensioning device, a reciprocatory Huid-pressure engine connected thereto, a relief vent in said engine adjustable to allow escape of pressure fluid at a predetermined rate, and means responsive to fluctuations in the load on the belt drive for adjusting the fluid pressure tovary the position of 'the 'belt tensioning device.

The foregoing specification signed at Glasgovv, Scotland, this 14th day of June, 192

p THMAS CAYGlLL LENNARD. 

